Introduction
In this chapter we will discuss the remaining diatonic traids and how they function.
This includes the mediant, submediant, and leading tone triads.
Before this lesson begins, a quick reminder of a few topics that will be relevant.
What are the Diatonic Triads?
In Music Theory I, you should have learned about how a triad may be built on any scale degree, and based on that scale degree, it gets a different roman numeral.
The triads that we covered in Music Theory I are...
| Function | Quality (Major) | Quality (Minor) |
|---|---|---|
| Tonic | Major | Minor |
| Subdominant | Major | Minor |
| Dominant | Major | Major |
| Supertonic | Minor | Dim. |
Wait, you keep using the word function all over the place, what does it mean???
The word function refers to two things:
The formal name of the triad. Example: the submediant triad refers to the traid build on scale degree 6. Even though in the major scale and minor scale, they are entirely different chords, they still act identically to eachother, therefore they get the same name.
There is also a generic function. All chords map onto one of the three generic functions as well: Tonic, Dominant, and Predominant
- Tonic has Tonic function and Dominant has Dominant function. These are obvious.
- Subdominant and supertonic are both Predominant chords. (Notice they both commonly have Fa in the bass, too. That isn't a coincidence)
But if they both have the same generic function, are they interchangeable? Yes and No. We will cover that in this lesson.
Cadences
It will be helpful to remember what a cadence is. We define three cadences
- The Perfect Authentic Cadence (PAC), root position V to root position I with Do in the soprano at the end of a phrase
- The Imperfect Authentic Cadence (IAC) root position V to root position I without Do in the soprano end of a phrase
- The Half Cadence (HC) root position V at the end of a phrase
Before you ask....
- Yes, they have to be root position.
- No, there is no plagal cadence
- Yes, the IV - I pattern exists near cadences but it doesn't articulate phrases. Wait until the forms class for more info on this.
- Yes, the "end of a phrase" part of the definition is very important and part of the definition. Otherwise you could mark a cadence every single time V to I shows up, and that just isn't accurate.
- Yes, an authentic cadence can also have V7 instead of V
- Yes, a half cadence can have V7 but it is much less common than you would think.